From Austrian Patent Disclosure AT-B 396210, a welding machine of this generic type for producing wire grid mats comprising longitudinal and transverse wires crossing one another and welded together at the crossing points is known. The welding machine has a connecting piece, which penetrates the grid production plane and is solidly connected to the upper electrode and forms the electrical connection of the lower electrode to the welding transformer. For positioning the electrodes transversely to the production direction, the lower electrode is docked to the upper electrode, and the lower electrode is additionally connected to the connecting piece, creating a rigid welding head. Simultaneously with the connection of the electrodes to form a rigid welding head, this welding head is detached from the common rails. The welding head is coupled to the conveying direction and then moved transversely to the production direction. This welding machine has the disadvantage that the grid production plane is penetrated by the connecting pieces, and positioning of the electrodes can therefore be done only once all the longitudinal wires have been removed from the range of motion of the electrodes.
Also from Austrian Patent Disclosure AT-B 332198, a device for delivering the welding current to welding electrodes in a multi-point grid welding machine that has at least two common rails extending across the machine width transversely to the production direction is known. This device has an adjustable switch member that depending on its switching position connects one of the common rails at a time selectively to the lower electrodes. A disadvantage of this device is the fact that because the common rails extend over the machine width, the welding current paths are of different lengths for different longitudinal wire diameters.